1. Technical Field
The invention relates to an illumination system used in a projection apparatus and a projection apparatus using the illumination system.
2. Related Art
A projection apparatus is a display apparatus used for producing large size images. An imaging principle of the projection apparatus is to convert an illumination beam generated by a light source into an image beam through a light valve, and project the image beam onto a screen or a wall through a lens to form an image. Along with development of projection technology and reduction of fabrication cost, usage of the projection apparatus has gradually extended from commercial use to family use.
The conventional projection apparatus generally uses a high-pressure mercury lamp as a light source (for example, an ultrahigh-pressure gas discharge lamp), though a large amount of emitted heat thereof limits a life time of the high-pressure mercury lamp. Compared to the high-pressure mercury lamp, a solid-state light source (for example, a light-emitting diode (LED) or a laser diode (LD)) has a longer life time and occupies less space.
The projection apparatus generally uses a heat sink in collaboration with a motor fan to cool down the light source, which is adapted to both of the high-pressure mercury lamp and the solid-state light source. However, a problem of friction loss is generated between a shaft and a bearing of the motor fan. Usage of an oil-contained bearing may cause pollution, and a magnetic shearing sound caused by rotated motor fan and a wind shearing sound caused due to contact of rotated fan blades and air may all produce noise.
U.S. Patent Publication No. 20050077103, China Patent Publication No. 100437343 and U.S. Pat. No. 7,407,293 disclose a technique of cooling a “high-pressure mercury lamp” by using an ion wind generator to produce a forced convection air.